The invention relates to a compressor comprising a scroll compressor with a first compressor member and a second compressor member, first and second scroll ribs, respectively, of which are designed in the form of a circular involute and engage in one another such that the second compressor member can be moved in relation to the first compressor member on an orbital path about a central axis, a drive for the scroll compressor with a drive motor and an entraining unit which has an entraining member driven by the drive motor and moving on an entraining path about the central axis and an entraining member receiving means arranged on the second compressor member, wherein the entraining member receiving means can be moved in a radial direction in relation to the central axis with a radial degree of freedom in relation to the entraining member such that the second compressor member can be moved so as to abut sealingly with the second scroll rib on the first scroll rib of the first compressor member on account of the radial degree of freedom and the centrifugal forces acting on the second compressor member.
A scroll compressor of this type is known, for example, from U.S. Pat. No. 5,295,813.
The problem with these scroll compressors is that this solution is complicated to produce and, on the other hand, undesired, high, local area pressures can occur due to the flat entraining member surfaces.
The object underlying the invention is therefore to improve a compressor of the generic type in such a manner that this can be produced as simply as possible and operates as reliably as possible.
This object is accomplished in accordance with the invention, in a compressor of the type described at the outset, in that the entraining member has an entraining member surface curved convexly in a direction transverse to the central axis in a direction of rotation, that the entraining member receiving means is non-rotatably arranged in relation to the second compressor member and has an entraining surface which surrounds the entraining member in a ring shape and on which the entraining member surface bears by always acting upon it with a force only in a subsection, that during movement of the second compressor member on the orbital path the subsection acted upon with a force likewise moves on the entraining surface and that a space allowing the radial degree of freedom of the entraining member receiving means in relation to the entraining member exists between the entraining member and the entraining surface outside the subsection acted upon with a force.
The advantage of the inventive solution lies in its constructional simplicity which allows the entraining member receiving means, on the one hand, to be arranged on the second compressor member so as to no longer be rotatable but rather non-rotatable so that the rotary bearing required for this can be omitted since in the inventive solution the relative rotation is accomplished by the movement of the subsection on the entraining surface.
In addition, the inventive solution has the great advantage that it requires less parts and, in particular, only parts which are easy to machine.
A particularly simple solution from a constructional point of view provides for the entraining member receiving means to be securely arranged on the second compressor member.
In the constructionally simplest case, this is a bushing which is preferably integrally formed on the compressor member, the entraining member engaging in its inner recess.
With respect to the dimensioning of the possible radial degree of freedom it would also be conceivable to design this to be smaller than the maximum possible movements of the compressor member in a radial direction. It is, however, particularly favorable when the possible radial degree of freedom corresponds at least to the maximum deviation of the orbital path of the second compressor member from a geometrical circular path around the central axis. In this respect, the geometrical circular path around the central axis represents the ideal case of the orbital path which cannot, however, either be achieved from time to time or be maintained over a longer period on account of the manufacturing inaccuracies in the area of the scroll ribs, on account of thermal changes during operation, for example, varying temperature expansion or also on account of wear and tear and so it is to be assumed that the actual orbital path of the second compressor member deviates from the ideal geometrical circular path.
With respect to the dimensioning of the space it is particularly favorable when the space has in a radial direction an extension which corresponds at least to the maximum deviation of the orbital path from the geometrical circular path since, as a result, the space is in a position to allow the radial movements which are necessary so that the second compressor member always extends with its second scroll rib so as to lie along the first scroll rib of the first compressor member.
In a preferred embodiment the space has a dimension which is in the range of approximately 1.5‰ to approximately 15‰ of an extension of the entraining surface in a respective radial direction. Values of approximately 2‰ to approximately 10‰ are preferred.
With respect to the design of the space the most varied of solutions are conceivable. It would, for example, be conceivable for the space to become suddenly wider following the entraining member surface.
However, in order to provide for the fact that during a radial movement of the entraining member receiving means relative to the entraining member the radial movement is subject to a certain attenuation, it is preferably provided for the distance between them proceeding from the subsection acted upon with a force to become increasingly larger with increasing distance from the subsection, i.e. due to the continuous increase in the distance between the entraining member surface and the entraining surface a lubricant cushion forms close to the subsection acted upon with a force and this has to be expelled from the space during a sudden radial movement and thus a certain attenuation effect begins.
In this respect it is particularly favorable when the distance between the entraining member surface and the entraining surface on both sides of the subsection acted upon with a force increases with increasing distance from it so that a movement in a radial direction and also in the opposite direction thereto experiences a respective attenuation.
A particularly favorable solution with respect to the production of the entraining surface provides for the entraining surface to extend in a circular shape, preferably as a cylinder surface of a circular cylinder, so that during the movement of the second compressor member on the orbital path the entraining member surface moves along the entraining surface extending in a circular or cylindrical manner.
In this respect, the center point of the circle or cylinder formed by the entraining surface is preferably located on the circular path around the central axis which underlies the orbital path.
With respect to the design of the entraining unit, no further details have been given in conjunction with the preceding explanations concerning the invention. A most simple embodiment of an inventive entraining unit provides for this to have a single entraining member surface and an entraining surface associated with it. The space is preferably located between the entraining member and the entraining surface.
Another advantageous solution provides for the entraining surface associated with the entraining member surface to be arranged on an intermediate ring which, for its part, bears with an additional entraining member surface on an additional subsection of an additional entraining surface by acting upon it with a force and for an additional space contributing to the radial degree of freedom of the entraining member receiving means in relation to the entraining member to likewise exist between the intermediate ring and the additional entraining surface. The advantage of this solution is to be seen in the fact that it is possible to divide the radial degree of freedom which can be obtained altogether between at least two or more spaces so that these spaces can, for their part, be kept as small as possible in order to achieve as good a lubrication as possible in the area of the spaces but, on the other hand, the radial degree of freedom possible altogether in a radial direction can be as large as possible on account of the sum of the widths of the spaces in a radial direction.
With this embodiment it is not absolutely necessary for the intermediate ring to slide along the additional entraining surface with the additional entraining member surface. It is also conceivable for the intermediate ring to roll on the additional entraining surface with the additional entraining member surface.
As for the rest, it is also conceivable within the scope of the inventive solution for the entraining member surface to roll on the entraining surface even with only one entraining member surface and one associated entraining surface which does, however, make it necessary to realize the entraining member surface, for example, as an outer surface of a sleeve surrounding the entraining member and rotatably mounted on it so that the entraining member surface can, as entire outer surface of the sleeve, roll on the associated entraining surface during the movement of the second compressor member on the orbital path.
For reasons of as inexpensive a solution as possible it is, however, particularly favorable when at least one of the entraining member surfaces slides relative to the associated entraining surface during the movement of the second compressor member on the orbital path since this solution is particularly simple to realize and also allows a large degree of freedom with respect to the design of the member bearing this entraining member surface.
In the case of an entraining member surface sliding on the entraining surface it is important to have an optimum lubrication which can be obtained when a hydrodynamic lubrication film can be generated between the sliding entraining member surface and the associated entraining surface, this film contributing to the fact that no essentially linear abutment takes place between the entraining member surface and the entraining surface but rather the entraining member surface bears over an area with a greater expansion on account of the lubrication film.
For the formation of such a lubrication film it is particularly favorable when lubricant is supplied in front of the entraining member surface when seen in the direction of rotation of the entraining member so that the lubricant is moved during the rotary movement in the direction of the subsection acted upon with a force.
In this respect, it is particularly favorable when the supply of lubricant takes place via the entraining member.
Such a supply of lubricant to the entraining unit via the entraining member may be realized in the most varied of ways. It would be conceivable, for example, to allow lubricant to exit at the end side of the entraining member, this lubricant then moving in the direction of the space and passing into it. A particularly favorable solution provides for the entraining member to be provided for this purpose with a lubricant channel passing through it, wherein the lubricant channel preferably continues from the entraining member via the drive shaft and a lubricant pump is arranged, for example, at an end of the drive shaft of the drive motor located opposite the entraining member.
In order to achieve a particularly precise lubrication, it is preferably provided for the entraining member to be provided with a lubricant outlet opening opening near to the entraining member surface and into the space so that the lubricant is preferably introduced into the space directly in front of the entraining member surface and then moves from the space in the direction of the subsection acted upon with a force.
With respect to the design of the space, the most varied of possibilities are conceivable. However, in order to have the lubricant available in the area of the subsection acted upon with a force in as optimum a manner as possible, particularly for forming a hydrodynamic lubrication film, it is preferably provided for the space to have in front of the entraining surface when seen in the direction of rotation of the entraining member an extension which holds the lubricant on account of a capillary action.
It is even better when the space has over its entire extent such an extension that it holds lubricant on account of a capillary action.
With respect to the alignment of the entraining member surface in relation to the direction, in which the radial degree of freedom is effective, particularly in the direction of a connection line between the central axis and a contact line of the scroll ribs, no further details have so far been given.
It is, for example, particularly advantageous when the subsection of the entraining surface acted upon with a force always extends approximately parallel to the direction of the radial degree of freedom and retains this alignment so that, as a result, a defined alignment of the effect of the entraining member on the entraining member receiving means can be determined. In the ideal case, the subsection lies symmetrically to a tangent to the circular path underlying the orbital path, wherein the tangent extends through the center point of the circular entraining surface. In this case, the entraining member always acts on the second compressor member in such a manner that it is in a position to overcome the tangential gas force but does not make any contribution whatsoever towards the radial degree of freedom and so the radial gas force merely counteracts the centrifugal force.
It is, however, also conceivable to determine the subsection of the entraining surface acted upon with a force such that this has a slight inclination in relation to the direction of the radial degree of freedom and thus the fact that the tangential gas force is overcome by the entraining member leads either to an additional force component acting radially outwards in addition to the centrifugal force or to an additional force component acting radially inwards.
Additional features of the invention are the subject matter of the following description as well as the drawings illustrating several embodiments.